Hurray for science! Thanks to it and people who believe in it, a small tan spore that has been sprouting happily for Bay Area trippers for decades has a name: Psilocybe allenii. Our friends at the Psychedelic Society of San Francisco  tipped us off to the fact that PSSF lecturer and mycologist Alan Rockefeller had helped pen a definitional paper that introduced the little guys. Rockefeller will be leading a Society mushroom hunt -- open to all comers -- in Golden Gate Park on Thu/20 . He told us hippies have been hunting Psilocybe allenii in the park for ages, previously using its informal name Psilocybe cyanofriscosa, which sounds suspiciously close to "San Francisco" to us.
We got in touch with Rockefeller and his cohort Peter Werner by email to hear about our new fungal friend. They only used a few words that we didn't understand, but we're willing to put up with it because they are very smart people.
PLEASE NOTE: Do not eat wild mushrooms without someone who knows what they're doing. Really. 
San Francisco Bay Guardian: How was Psilocybe allenii discovered?
Alan Rockefeller: [John W. Allen] found it in wood chip landscaping [where it grows] October through January. It grows in cities, in areas where lots of people go. John is not the first person to find the mushroom, it has been well known for a long time. It was named after him because he picked it and mailed it to [Czech mycologist] Jan Borovicka. The earliest collection that I know of is a photo by Paul Stamets, taken in Golden Gate Park in 1976, and published in Mushrooms Demystified by David Arora. In that photo, there are three Psilocybe cyanescens and three Psilocybe allenii, all labeled Psilocybe cyanescens.
It's been an open secret for many years that there is a new psilocybin mushroom that needs to be described. Literally hundreds of people have found it. People have been calling it "Psilocybe cyanofriscosa" since 2006, but that name is not proper Latin and was never validly published. New species of mushrooms must be named using proper Latin, and need to be described in a peer reviewed scientific journal.
SFBG: How was it determined to be psychedelic?
AR: All mushrooms which stain blue where damaged and have either a dark purple brown or black spore print  are psychedelic.
This species has been eaten by many psilocybin mushroom enthusiasts and they say it's one of the strongest mushrooms known. The only mushroom which may be stronger is the closely-related Psilocybe azurescens. That species is very similar but has a cap that is umbonate, and there is a two base pair difference in the ITS gene. Psilocybe allenii occurs from BC, Canada to Los Angeles, and is common in San Francisco. Psilocybe azurescens only occurs within 20 miles of the Oregon/Washington border, in coastal dune grasses in the mouth of the Columbia river. (Correction: John W. Allen wrote to us to assure us that Psilocybe azurescens grow quite prolifically in the Seattle Puget Sound area)
Psilocybe cyanescens is also very common in San Francisco. It is almost as potent. If you go to Golden Gate Park in December you will see hundreds of hippies looking at the wood chip landscaping for Psilocybe cyanescens and Psilocybe allenii.
SFBG: How common is it to find new psychedelic/otherwise mushroom strains?
Peter Werner: Mushrooms in general? Finding new species is quite common, because fungi are not nearly as well investigated as plants, in spite of being a kingdom that, if anything, contains more species. (Albeit, mushroom-forming fungi are a small subset.) I couldn't give you exact numbers, but there are probably a number of new species described in California each year. In really mycologically-underexplored areas, say Belize or Guyana, a mycologist may make a large collection in an hour, over half of which will be species that have never been scientifically described. Dennis Desjardin, the eminent mycologist at SFSU, once said that if he never went out in the field again, he could spend the rest of his life naming undescribed species deposited in the SFSU herbarium.
In terms of Psilocybe in this part of the world, people find new species less often, because most of the West Coast species were described during a great wave of interest in the 1960s and '70s. Still, there are several papers each year describing new Psilocybe species from various parts of the world, including from North America.
SFBG: How many species of mushrooms are there?
PW: [First you have to not just] define "species." but define "mushroom"! The terms "mushroom" and "truffle" describe pretty much any macroscopically visible fungus with a distinct fruiting body, that are above-ground or underground, respectively. But definitions vary -- the terms are not scientific ones. To take a stab at the number, I'd say the majority of mushroom and truffle species fall into the basidiomycete subdivision Agaricomycotina, and the Tree of Life web pages  (which are a good general source for such things) estimates some 20,000 named species. (Named being the keyword here, undescribed species making up a possibly much greater number worldwide.) There are another about 1700 named species in the order Pezizales, which include the majority of fleshy ascomycetes (morels, cup fungi, true truffles, etc.)
In terms of fungi in general, that runs into the many millions, most of which are unnamed. Estimates range from over 600 thousand to over 5 million. A good article on estimating the earth's biodiversity, including estimates of fungi, was run in the New York Times science pages last year .
SFBG: Are there any events coming up that laypeople might be interested in/invited to? Do you have to be a mushroom expert to be a part of the Society?
AR: I am leading a mushroom hunt in Golden Gate Park on Dec. 20 at noon, it is open to the public. You don't need to be a mushroom expert to attend. I think that I am the only mushroom hunter that attends these events. Information on where exactly to meet will be posted on the SF Psychedelics Society website .